Apparatus for igniting and operating gaseous discharge devices



APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE DEVICES Filed lay a, 1959 r a Sheets-Sheet 1 Oct. 3, 1961 E. J. HUBERTY ET'AL ,0 3, 1.

amey

Oct. 3, 1961 E. HUBERTY EIAL 3,

APPARATUS FOR IGNITING AND OPERATING GASEOUS nxscumcs onvrcss 7 Filed May 6. 1959 3 Sheets-Sheet 2 M INVENTURS.

I am? Oct. 3, 1961 E. J. HUBERTY EI'AL 3,003,031

APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE usvrcss 3 Sheets-Sheet 3 Filed llay 6, 1959 2r r/ME United States Patent O ice 3,003,081 I r APPARATUS FOR IGNITING AND OPERATING v x GASEOUS DISCHARGE DEVICES Elmer J. Hnhcrty and Albert E. Feinberg, Chicago, Ill.,

assignors to Advance 'Ihns'former 'Co.,-- Chicago, 111.,

a corporation of Illinois I Filed May 6, 1959, Ser. No. 811,297

22 Claims. (CL 315-257) This invention relates generally to apparatus for igniting and operating gaseous discharge devices, and more particularly is concerned with the construction of a transformer for use in a gaseous discharge device system and with the system itself, in which the source of electrical power for the system comprises an AC. line subject to variation and fluctuation in line voltage, the invention being specifically directed to structure providing substantially constant vwattage or current flow through the gaseous discharge devices. g

The primary purpose for which the invention herein was made was for application to gaseous discharge devices providing visible light output for illuminating purposes although the invention may be applied to other gaseous discharge devices. The gaseous discharge devices which provide visible light are of several types, important of which are cold and hot cathode fluorescent lamps and metallic vapor lamps utilizing the visible radiation from mercury or sodium vapor -or the like for their light output. a

All gaseous discharge devices have in common several characteristics which are unique. The gaseous discharge device is a negative resistance device in that when it is operating, that is, a current is flowing through the same, its resistance decreases with voltage so that unless in someway prevented fromdoing so, the current will increase at a rapid rate until the devic'e'becomes practically a short circuit and either destroys itself or the conductors andcircuit elements with which it is connected. Gaseous discharge devices are therefore ballasted, that is, provided with impedance to flow of current which limits the current to some predetermined value established as rated for the device operating at maximum etliciency and for longest operative life. Another characteristic of gaseous, discharge devices is that all have a much higher igniting voltage than operating voltage. The discharge through the gaseous discharge device which gives rise tothe radiation is an ionization of gas within the envelope of the device and this gas must be broken down before there is any flow of current, comprising the ionization current. Thus, a high open-circuit voltage must be applied to the device, this voltage being higher than the operating voltage, and in most modern dischargedevices being substantially greater than the line voltage. Once the lamp has ignited, ,it is essential that the voltage applied to the lamp dropto its operating value. 7

A system for igniting and operating gaseous discharge devices is ideally constructed using a transformer which has high leakage reactance deliberately built into the transformer so that upon open-circuit when there is substantially no current flowing in. the output portion of the transformer the leakage reactance has a minimum,

effect, and the voltage is high;-but when the discharge device has ignited and currentflows in theoutput circuit. the leakage react-ance effect is substantial and the voltage;

decreases.

Various structures have been devised for assistingflin the ignition of the devices, for providing suitable voltages for different kinds of devices andthe like. Includedin these structures have been those of the constant current or constant wattage type, in which the gaseous discharge load is desired to be operated at a constant current ir- Patented Oct. 3, i 1961 2 respective of substantial variations in the line voltage. These have been especially intended for use with the cold cathode type of discharge device and with the metal lic vapor devices, although advantageously they can be used as well with ordinary fluorescent lamps.

The fluorescent lamp which is most familiar is a glass tube having a small quantity of ionizable gas therein, usually argon together with a small quantity of mercury, at a relatively low pressure such as 2 to 3 mm. ,and the walls ofwhich are coated with phosphors which fluoresce when subjectedto the ultra-violet radiation from the gas.

The cathodes of such lamps are usually of the hot type,

trons at relatively low voltages, with nominal voltage drop at the cathode. This drop for a lamp having an operating voltage of 195' volts may be at most 15 volts.

In the case of cold cathode lamps, the cathodes are substantially larger in size than those of the hot cathode lamps, and are not heated to incandescence. Instead, it is believed, the electrons providing flow of current are knocked out of the cathode by positive ion bombardment, and hence amuch higher voltage is required for the operation of such lamps. The cathode 'dropin a cold cathode lamp is very substantial and sufficient part of the total voltage drop across the lamp to be consid: cred important in any given circuit. For example, a typical cold cathode lamp operating at a total voltage of 420 volts will lhave acathode drop of about :105 volts. Obviously the greater the cathode drop the less the voltage available for light-producing discharge, which is in effect a flow discharge instead of anarc discharge as in the case of the hot cathode lamps. 1

It has been found that the cathode drop increases with age. Thus, for this reason, and in addition for compensating for the variations in line voltage, it is essential for the operation of cold cathode lampsthat the current be maintained at a substantially constant value.

Cold cathode lamps usually have phosphors on theinterior surfaces of their envelopes to fluoresce when bombarded by the ultraviolet rays of the glow discharge I of the mercury or other gases which are also contained within the envelopes at low pressures. As in the case of ordinary fluorescent lamps, cold cathode lamps may contain argon or other inert gas at a pressure of about 2 or 3 mm. with a droplet or two'of mercury suitable for vaporizing once the discharge has started.

7 Metallic vapor lamps are of the hot cathode type and usually have a gas therein at substantial pressure, such as for example, several atmospheres, and depend upon the arc discharge itself for the production of light. A pool of the metal heated by passage of current may initiate the discharge. Such lamps provide great brilliance and operate at relatively high temperatures. Theirenvelopes and seals are subjected to unusual stressesand hence great care must betaken to assure that the rated current flows in the lamps. Too high a currentincreases the temperature'of the lampand its seals, andtoo low a'current decreases the light output. 'Obviously, such lamps are best operated at constant current, so that their life is prolonged and elficienc'y maintained.

An additional reason for using circuits and structures such as those of the invention for metallic vapor lamps is that suchlamps are usually installed in street and high- Way lighting systems in which the lamps are spacedsubstantial distances apart and the voltage drop in the feed lines is not readily maintained constant, but varies with many conditions.

There have been constant current or wattage devices Which depend upon the saturation of an iron core to limit the voltage or current which is "supplied to the load. The structures of the prior art have been built with the belief that in order to achieve the desired results it has been necessary to saturate both the primary and secondary core portions of the steel or large portions of the core. Such structures that used small total core crosssections have not utilized a series condenser to assist in the saturation of the 'core under the secondary winding.

The invention herein is based upon the discovery that the regulation canbe achieved in a circuit having a capacitive reactive character by saturating only a very small portion of the total core length of the central winding leg under the secondary winding, but providing sulficient axial length for the saturated portion so that there is no possibility of the core acting as though it had an ordinary wave-shape-correcting bridged gapfth'er'ein. The general proportions will be described'inthe detailed specification hereinafter.

Theadvantages of saturating only a very small portion of the core and nevertheless achieving the desired regulation relate to the core loss attendant upon high flux densities. In previous devices, it has been found that Where the central Winding leg is of the same cross sectional area throughout that the core loss of the steel exceeds even the copper loss.

The invention contemplates the saturation of only a small portion of the central winding leg and hence the core'loss of steel is considerably reduced because of the small portion that is actually saturated.

It is the primary object of the invention to Provide a transformer-and system for igniting and operating gaseous discharge devices in which the output of the transformer is connected into 'a capacitively reactive load, and in which the current flowing in the load will be substantially constant irrespective of variations in line voltage energizing the circuit and irrespective of variations in the load characteristics, the said transformer having less losses than prior structures.

A further object of the invention is to provide a structure of the character described in which the noise and fringing of stray and extraneous flux'is keptto a minimum because of the manner in which saturation is obtained in only that section of the core which is completely confined within the secondary winding.

Other objects of the invention are concerned with the various phases of the invention which will be brought out hereinafter, and these and other advantages of the invention will become apparent to those skilled in this art as the detailed description of preferred embodiments proceeds, in connection with which there are attached illustrations, more or less diagrammatic in nature, but which are fully understood by the skilled artisan.

In the drawings,

FIG. 1 is a sectional view taken through a ballast for igniting and operating gaseous discharge devices constructed in accordance with the invention, the view being somewhat diagrammatic and illustrating the transformer of the invention in plan aspect with a fragmentary portion of the canister and potting compound of the ballast being also shown.

FIGS; 2 and 3 are electrical circuit diagrams of two circuits for gaseous discharge devices either of which is capable of being used with the ballast of FIG. 1, the circuits being characterized by the fact that each circuit ignites and operates two series pairs of discharge devices.

FIG. 4 is a fragmentary view somewhat similar to that of FIG. 1 but showing only the'left handend of a modified form of the invention.

FIG. 5 is a fragmentary view similar to that of FIG. 4

4 and showing the left hand end of a still further modified form of the invention.

FIG. 6 is an electrical circuit diagram of a single gaseous discharge device apparatus utilizing the invention.

FIG. 7 is a view similar to that of 'l but of a modified for'm of structure 2601- use with the circuit of FIG. 6. 1 1

FIG. 8 is a diagram of the current wave in the secondary winding of a transformer of the constrnet-ien of the invention.

The invention is characterized by providing aniron core having a central winding leg upon which the Windings of the transformer are wound, and there being at least a primary winding and a secondary winding, coaxial with the central winding leg and separated from one another by a shunt, such as for example, a magnetic shunt having an air gap and thereby providing the desired leakage reactance above referred to. The outer framing portions of the iron core comprise parallel outer legs spaced from the central winding leg on opposite sides thereof and forming windows within which the windings are located, and the ends of the outer legs having end portions directed toward and abutting the ends of the central Winding leg on-o'pposite edges thereof.

The general configurationof the transformer is completely conventional, in that any of the well known structures including core type and shell type cores may be used. In the case of the conventional shell type transformer core, which is usually preferred, the width ofthe central winding leg is twice the width of either of the outer legs, and the end bridging portions have the same width (measured along the axial length of the central winding leg) as the transverse width of the outer legs. Because of the structure thus far described, all of the benefits of scrapless stamping of the laminations and economical production may be obtained. The width of the central winding leg is the same under the secondary as it is under the primary winding. The invention will be described in connection with shell type cores.

According to the invention, the portion of the central winding leg which is disposed completely on the interior of the secondary winding is reduced in cross sectional area in an amount which provides-the localized saturation that has been found effective to provide satisfactory regulation of the apparatus when one or more gaseous discharge devices are connected in the output of the secondary winding in a capacitive circuit. Thisioealized reduction in area has substantially the same effect as reducing the entire cross sectional area of the central Winding leg-and as amatter of fact, it may be stated that the excellent results achieved with the invention herein have 'proven that the prior structures which actually reduced the entirewinding leg were constructed upon the basis of an erroneous assumption that such total saturation was necessary and hence introduced unnecessarily large amounts of saturation and large losses in such cores.

The reduction in cross sectional area at a localized part of the central winding leg may take any of several dinerent forms, the most effective of which were found-to be a single rectangular center opening, a group of notches along opposite edges, and a group of slots in the center. The cross sectional area at such part of the centralwind ing leg is completely within the secondary winding and is reduced about 25% to 50% of its original area. This comprises decrease in transverse dimension across the center winding leg by the removal of metal. As for the axial dimension, that is, length along the center winding leg, of said removed portion of the metal, it should be suflicient to prevent excessive bridging'of the'flux. The total axial length of the'openings orgaps or notches found desirable and effective has been approximately one to oneand one-half the total'reduction in then-ansversedimension. Dimensions may vary dependingu'pon The projections 38 40, cooperating with the bridging ends 42 and 44 provide windows 64, 66 and 68 along the length of the core 32, there being conforming pairs of windows on opposite sides of the said winding leg 46.

to 20,000-gauss. Increasing the flux density substantially above 20,000 gauss produces a tendency for the reduced section to permit flux bridging the air space remaining at the reduced section, and in addition may saturate the entire core at a relatively low level which produces the same eficct as a continuous air, gap without the presence of steel. In the case of such latter-mentioned effect,

' there would be a linear change of flux with variations of load or primary voltage, which is the opposite to that which it is desired to achieve. In such cases, excessively lengthening thereduced area along the axis of the central winding leg will increase the amount of steel operating at high flux densities and thereby also defeat the purpose of the invention by excessively increasing the losses. i

The dimensions of gaps of structures such as Berger Patent'2,461,957 transversely ofthe center winding leg or core element wherein located are normally substandaily in excess of 50% of the. width of the central winding leg, and considering the axial dimension along the length of the winding leg are substantially less than 25% of the transverse dimensional width of such gaps. Thcsegapsact in the manner described above in connection. with the phenomenon at high flux densities, namely-the flux may pass across these gaps readily and give linearity to the total flux path, for correction of wave shape. The ideal gap of this type has no bridging portions, the ends of the gaps being small as mechanically feasible so that there is saturation at relatively low primary voltages to give the effect of'a complete air gap. The invention herein operates on a totally different principle, since the remaining portions of the reduced area sections must have the desired saturation to give the regulation needed for maintaining constant current in the load. r

In FIG. 1 there is illustrated a ballast, designated generally by the reference character 10, which is designed for use with either of the circuits 20 or 30 shown in 'FIG. 2 or 3v respectively, The ballast includes an iron core transformer 22 which is disposedxwithin a metal camster; 24 being potted therein with suitable potting Q0111? pound 2:6 along with other elements some of which are shown in the circuit diagrams of FIGS. 2 and 3. The transformer. 22 in this case comprisesa shell type core which may be designated generally 32 and is formed of. a pair of outer legs 34 and 36 each having inwardly. extending projections 38 and 40 juxtaposed relative to one another respectively andinwardly extending bridging end portions 42 and 44. There is a central winding leg 46 which is engaged between the two outer legs 34 and 36, extending the entire length thereof. The 'bridging end portions 42 and 44abut against the opposite edges of the central winding leg 46 adjacent the ends thereof in the abutting joints 48 and 50 which may be considered efficient magnetic connections." Notches cut at 52 at the corners of the outer legs. 34 and 36 seat clamping. members generally shown at 54 for maintaining the entire transformer inassembly. V

Withoutgoing into great detail, zit should be pointed out that theside legs 34 and 36 and the central winding leg 46 are all formed of thin laminations of electrical sheet steel, such as silicon or cold rolled steel, all in the manncr well known in this art. f y l I The projections 38 and 40 are not long enough to abut the .sideedges of thecentral winding leg 46 and hence form non-magnetic gaps at: 56 and 58 which may bepermitted to remainas air gaps or may be filled with such'gap-fillingmaterial as well known. The projectionsand their air gaps form the two magneticshunts 60 and 62; Y I

Each pair of windows on opposite sides of the central winding leg has a winding disposed therein, these windings being, respectively, right. to left, a secondary winding S a primary winding P, and a secondary winding 8,. These windings are tubular in configuration and are all coaxial with the central winding leg46, being spaced along the 1 length thereof. The windings are suitably insulated in accordance with known techniques, and each completely encloses a different portion'of the central winding leg;

Attention is now invited tothe relative dimensions of the structure of the core 32. The width (up and down) of the central winding leg 46 transversely of its axis (right and'lcft) is designated by the character A; the widths of each of the outer legs-34 and 36 are similar and this dimension is designated B; the widths (transverse dimension) of eachof the bridging portions 42 and 44 are the same and are designated 'C. The dimensional relationhold true here, namely, B=C and A=2B.

The difference between'this above describedstructure and known structures lies in the construction of the core portions under the secondary windings S and S Since both are substantially the same, only the structure under S need be described. The central winding leg 46 beneath the secondary winding S is designated 70 and aswill be seen there is a series of notches 71, 7 2 and 73: out along opposite edges of the central winding leg, each pair of opposite notches beingtransverscly aligned, so that the reduction of the cross section area of the portion 70 at each pair of oppositenotches is measured by twice the depth D of the notches. The reduced area is A-ZD. In anactual example, the dimension A was 1.5 inches, and

ships of conventional core structures of this general type the notch depth D was .2 inch, so that the decrease or reduction was 26.7% leaving areduced area which was 73.3% of its former area. The notch width E was .156 inch so that the total axial length of the notched portions was .47 inch,which is 1.17 times the reduction of .4 inch or 31.3% of A. r

The structure'of FIG. 1 could be used in either one of the circuits of FIGS. 2 and'3.' In FIG. 2 the circuit 20 is a'straight transformer arrangement The primary winding P is connectedby the leads and 82 across a suitable A.C. 'line of proper voltage and frequency, such as for example a 120, 240m 277 volt A.C. line at'60 cycles.

One of the terminals of leads 80 and 82 may be connected to ground. V

The core 32 has shunts 60 and 62 positioned between the winding P and the respective secondary windings S devices is determined by the turns ratio between the primary winding and the respective secondaries as well as the coupling between the windings. When ignition has occurred, the voltages across the respective discharge devices drop' to a value'dependent upon the Ieakage react ance andthe total impedance ofthe respective circuits. These circuits are predominately capacitive so that a leading current flows in the secondary windings, which assists in the establishment of the desired saturation in the localized areas 70 of the central winding leg because iron in the vicinity of leading flux saturates more readily than iron in the vicinity of other flux.

- In the event that the voltage of the line sho ld or i other changes occur in the. circuit,,the -satur;ati on, ofi;-the core areas 70 will prevent changes in, the-currentflowing in the respective circuits.

In FIG. 3, the primary winding of the circuit-30 is connected from the lead 84 between the pairs of discharge devices L and L and the lead86-betweenthesecondaries S and S so that it isin autotransformerrelationship with each of the secondaries to, provide added'voltage; for ignition and operation of the dischargedevices. In,= al l. other respects the circuits function the same asthose ofi FIG. 2.

In FIGS. 4 and 5 there are ,illustrated two variations of the physical constructionof. the. transformer 22]. FIG, 4, the transformer 88 differsfrom the. transformer 22 only in the respect that instead of thenotchesfll, 72 and 73 there are provideda series of relatively large slots 91,, 92, 93 and 94 whose dimensions. are asstated above, namely their decrease of the area of; the central winding leg in; the vicinity 70;under the secondary windingS is from about. 25% to about andthe total cumulative axial length of the gaps, isfrom one toone and one-half times the total reduction, which in this instance comprises the transverse width F of the slots. F is equivalent of about .2D. The dimension betweenslotsmay vary and be control-led by the physical strengthdesired, the sizeof the apparatus and the like. All should be. confined within h ec nda y winding In FIG. 5, thetransformer 98is theequivalent of those.

described in FIGS. 1 and4, but is offthe forced-core type. Inthis type of, transformer, the outer legs 34, 36 and.the bridging ends only 44 of,.which is shown;comprise an integral closed, rectangular frame-like structure, and the windings are mountedon the centralwinding-leg46 which, isthereafter ,forced into thecenter ofthe framelikestructureto. abut the insideof. the.bridging ends as at 50. The coreisusually held together bymeans. ofarivets such. as at 100. Instead of either the. notches of. FIG. 1 or. the. slots Of'FIG. 4, the reduction inthe centralwinding leg at the section is achieved,throughtheuse. ofarectana gular, single cutout 101 ithe dimensionsof which again areasset forth above, namelythe transverse.v dimension of. the leg 46 is reduced from 25% to 50% ofsthe. width of.

the winding leg. andthe axialdimensionis. fromone. to one andzone-half. times the reduction.

As noted from. the above, the .circuits andtransformers described have been intendedfor use with.circuits which include. atv least two pairsof gaseous discharge devices. This. is .not intended. as a limitation since. either more or less .discharge devices-may -beused withsa single transformer. In FIGS. 6 and 7 the same structure as that shown-in FIG. 1 using-one-half of the circuit of FIG. 3 isilIustrated except for-use with a-single gaseousdischarge device. Also, a single notch171 has beensubstituted for all -notches 71, 72and 73. The ballast llllhas a transformer 122 which has only a primary winding- P and a secondarywi-nding S serving a lamp L in series witha condenser C The equivalent elements of the transformer122. have the same characters of reference as those of FIG. 1 but with the prefix 1. The-operation is the'same as-for either of the discharge device circuits of FIG.'3.

It has been found that thewave shapeof the current in the secondary of a device constructed according to the invention is somewhat as shown in FIG.-8, with a wave having a dip. This notonlyprovides goodlight-output and long lifefor the gaseousdischargedevice, but is also self-compensating. for changes. in .current .by changes in the.relativ.e .sizes. ofthemajor .and;'rr1inor peaks.

Another .importantbenefit .whichis achieved. through theuse of theinventiomand which is in addition to the principal purposeof the structure, is. that the location of the saturated portion. of.the; core. in.a portion of thecentral. winding leg completely enclosed; by. the secondary invention provlde constant wattage where required.

to the. anisterilt r; 124 mv her hyndec eues h .stantial variations in line voltage.

v and with the notched arrangement ofFIG. 1. The total length of the,core was 7 inches; the width was4 inches; the dimensionA Was 1% inches; the dimension B was 4 inch; the shunts-60.. and 62 were. .38v inch wide; the gaps 56and 58 were .05 inch; thewindows 64 and 68 were 1.624 inches; window 66 was 1.5 inches; dimension D was-.2 inch; dimension E was .156.inch; the distance between the notches was .219 inch; the transverse. dimen-.

sionsv of the windows was- /z inch each. The bridging ends, i.e., dimension C was slightly less than dimension ,B;-the distance from the left'hand. edge of, the notch 71 to the right hand: endof the central windingleg 46.was.

2 inches.

The.stackheightofthecore 32.was,1 inch; each secondary had 4600 turns of No. 32 gauge wire; the primary.

winding P-had 370 turns of No. 20 gauge .wire.

This transformer was connected into a circuit in which the line voltage across the primary winding; was 118 volts, 60 cycles; the secondaries wereeach connected to apair of commercially available hairpin-shaped cold cathode-fluorescent lamps 25 millimeters in diameter and 93 inches long, making a total of four lamps for the circuit. These lamps ignite at 750 volts, a series pair igniting at about 1350 volts; they operate at a voltage of 420 volts each, so that the drop across a pair is about 840 volts; they draw about 120 milliamperes and are rated at about 42 watts each. Each of the condensers C and C was a .21 microfarad condenser rated at 1600 volts.

The lamps ignited and operated satisfactorily for sub The voltage across each secondary was 1550 volts, and across the condenser 1240 volts. The circuit power factor was .95. Flux density measurements showed a 18,500 gauss in the saturated areas and a density of 14,500 gauss in the unsaturated areas.

To demonstrate the regulation of the circuit, choosing as. standard a line voltage of 118 volts, in varying the line voltage from about 99 volts to volts, the total variation of lamp current was not more than 2 milliamperes, which is approximately 2% total, or 1% on either side of average The invention is applicable to other circuits in which other than cold cathode lamps are used, and to apparatus in which the transformer is not necessarily of the shell type having a central winding leg. The teachings of the So-called core type transformers are often in the form of rectangular structures with the windings coaxial and disposed on dilierent portions of one elongate leg, the

3 other leg being disposed parallel to the winding leg and havingjno portions of the windings thereon. This structureas well as those structures in which the windings are divided in two and have half on each of the parallel legs, having the sameamount of flux threading each leg instead of having the central winding leg carry twice the flux as in either of. the outer legs: of :thestructures illustrated herein. The invention-is of course applicable to any of these structures and the provision of the localized saturated portion beneath the secondary windingcarry- "ing the leading current can produce the constant current apparatus desired. In the case of the structure with the half windings on the respective legs, the reduction of core will be provided under each half of the secondary winding, and in the case of the single secondary winding and unoccupied parallel leg, all of the reduction will be under the secondary winding.

In addition to variations in the structure of the transformer per se the circuits may; be. different from those illustrated. Also the form of the reductions may vary;

9; asfor example, using round Tnste'ad of-zrectangnlarconfigurationm] 1 I Some expression has beenmade. of the theories under which ittisbelievedcertain phenomena occur, but these are only intendedto assist in anunderstan'ding of the explanation; Notwithstanding that such theories may be incorrect, the structure which is described hereinabove and claimed hereinafter producefthe desired functions, irrespective of the basis for the operation thereof. No limitations are to be inferred from the statements of such theories, or the absence of others.

What it is desired to secure by Letters Patent of the United States is: V v

[1; Apparatus for igniting and operating gaseous .discharge means from a sourceof A.C; voltage which comprises an iron core transformer including an elongate flux conductive element, a primary winding and a sec-' ondary winding each coaxially mounted on a' different portion of said element and coupled relative one another to provide leakage reactance in the secondary winding during operation of said apparatus, said primary winding adapted to be connected to said source, a capacitive load circuit including gaseous discharge means connected with said secondary winding to have the current of said secondary winding flowing therein of leading character, the said element being of substantially uniform cross sectional configuration along the length thereof, and means for providing substantially constant current flow in said load circuit comprising a reduction of area of said portion of said element upon which said secondary winding is mounted of dimensions to provide a localized saturated portion of non-linear permeability confined between the-ends of said secondary winding.

2. Apparatus as claimed in claim 1 in which the reduction transversely of the element is at least approximately one quarter of the whole, and in which the axial eluding a capacitive reactor tive circuit with saidseconda'ry winding, and a-localized reduced area section in said flux 'path memberon-the interior of said secondarywinding to provide a saturated flux path in a portion of said 'tlux path membersubstantially less in length than the axial length ofvsaid secondary winding. 7 i

12. Apparatus as claimed in'claim 11 in which the saturated flux path is'less than'75% in area of the flux path member and has a length such as to .provide'nonlinear flux permeability in ,the said flux path member. 4 I

13. Apparatus as claimed in claim 12 in which the length of the saturated flux path is one to one and a half times the reduction ofthe area thereof.

14. Apparatus as claimed in claim -11 in which the said primary and secondary windings are connected inautotransformer relation. 1

15. Apparatus for applying the ignition and operating voltage to a gaseous discharge device from a source of AC. voltage at substantially constant current irrespective dimension of the reduction is at least one quarterthe width of said element.

3. Apparatus as claimed in claim 1 in which the flux density of the localized saturated portion during operation of said gaseous discharge means is between 18,000 gauss and 20,000 gauss.

4. Apparatus as claimed in claim 1 inwhich the reduction transversely of the element is from 25% and I 50% of the whole, and the dimension of the reduction along the length of'the element is from one to one and a halftimes the transverse reduction.

5. Apparatus as claimed in claim 4 in which the flux density of said localized saturated portion is from 18,- 000 gauss to 20,000 gauss eous discharge means. a

6. Apparatus as claimed in claim 4 in which said reduction comprises at least a pairiof transversely aligned notches onopposite edges of the said element.

7. Apparatus as claimed in claim 4 in which said re duction comprises a series of cut-outs in said element.

8. Apparatus as claimedin claim 7 in which said cutouts are notches onthe edges of said element.

9. Apparatus as claimed in claim 7 in which said cutouts are bridged slots in said element.

10. Apparatus as claimed in claim 4 in which said reduction comprises a single opening in the center of said element. 7 7 11. Apparatus for providing substantially constant wattage in a circuit for igniting and operating gaseous discharge means, which comprises an iron core trans former having a primary winding and a secondary winding, said'transformer having an elongate primary flux path. member of uniform cross section thereon coalong its length and the windings mounted thereon coaxially therewith and spaced from one another to proing adapted to be connected across a source of AC. voltage, means adaptedfor connecting said secondary winding in circuit with said gaseous discharge means induring operation of the gas-V rent tlow through said secondary winding during opera- I vide leakage reactance between them, said primary windof variations in the circuit, comprising a gaseous discharge device, a transformer having an iron core including a primary flux path leg, a primary winding connected to said source and mounted coaxial with said leg, a secondary winding connected to said discharge device and mounted coaxial with said leg, a shunt between said windings, a condenser in circuit with said secondary winding "and discharge device whereby the operating current in said secondary winding is predominantly capacii tive, said leg having substantially uniform cross sectional configuration along its length beneath both windings,

that portion beneath said secondary winding having a localized saturated section substantially less in length ial reduction being one to one and one-half times the transverse reduction.

18. Apparatus for supplying the ignition and operating. voltages to aplurality of gaseous discharge devices from a source of AC. voltage with substantially constant current flow in each of said gaseous discharge devices over a wide range of variation of circuit characteristicssduring operation, comprising at least two gaseous discharge devices, an iron core transformer having a primary windingand two secondary windings, each secondary winding being connected in a circuit with one of said gaseous discharge devices and having a capacitive reactor therein whereby to provide a leading curtion of said gaseous discharge device, a primaryflux conducting leg formed on said transformer and having uniform shape throughout its length, the primary winding being mounted on said leg in the center between the ends thereof and each of said secondaries being mounted on said leg on opposite sides of said primary winding andthere being a =gapped shunt between each secondary winding, and said primary to provide leakage reactance during operation of said discharge devices, said leg having restricted sections one confined within each secondary providing localized saturation during operation and non-linear flux permeability.

19. Apparatus as claimed in claim 18 in which said restricted sections are each formed by reduction of area of said leg both transversely of said leg and alongits lewh.

whereby to providea capabi 20. Apparatus as claimed in claim 18 in which said secondaries are both connected in auto-transformer relationswith said primary. 1 2 i 0 21. Apparatus as -clair'nedsin' claim 18 inrwhich sa-id restricted sections have a flux .density during operation of theorder of 18,00Qgausst0 20,000-igauss.

22. In apparatus for igniting and operatinggaseous discharge means wherein said apparatus includes: a source of AC. voltage, aniron core'transformer having a flux conductiveelement, primary'and secondary windings each coaxiallymounted ona difierentportion of said element and said windings being closely coupled one with the other to provide leakage reactance during the operation of said apparatus, said primary'winding being adapted to be connected to the said source, and a capacitive load circuit including said gaseous discharge means connected to said secondary winding'to have the current of said winding flowing therein of a leading character; the improvement r 12 consisting of. means fol-providing substantially constant current flow in said load circuit, said means comprising: a reduction 1 of cross-sectional area in said flux conductive element in the portion of said element upo'nwhich said secondary winding is mounted, said reduced area being of a dimension to provide a localized saturated portion of non-linear permeability entirely confined between-theends ofsaid secondary winding.

References Citedin the file of thispatent UNITED STATES PATENTS 2,346,621 Sela Apr. 11, 1944 2,432,343 Short Dec. 9, 1947 2,615,067 Bridges Oct. 21, 1952 2,648,802 Kazebee Aug. 11, 1953 2,664,541 Henderson Dec. 29, 1953 2,810,100 Strecker Oct. 15, 1957 

